As the ammonia-nitrogen wastewater is widely present in a variety of modern industrial production, the ammonia recovery from ammonia-nitrogen wastewater has the significance of resource utilization. Air-gap diffusion distillation is a novel heat separation method, which has the advantages of atmospheric pressure operation, simple structure, driven by low-grade thermal energy source and good economy. By numerical simulation, this work studied the process of ammonia recovery from ammonia-nitrogen wastewater based on the air-gap diffusion distillation. The effects of the structural and operational parameter on ammonia diffusion flux were analyzed. The results show that the ammonia diffusion flux increases as the decrease of the thickness of porous media and pore size of porous media; or as the increase of the inlet velocity of ammonia-nitrogen wastewater, mass fraction of ammonia-nitrogen wastewater and porosity of porous media.